Traffic sensitive spectrum access scheme for cognitive radio networks

A traffic sensitive spectrum access scheme is proposed to satisfy the traffic load requirement of secondary users （SUs）. In the proposed design, SU only accesses available channels which can meet the traffic demand. To achieve this, the expected transmission time （E3W） of the SU is calcu- lated first based on the delivery ratio. Then, the channel idle time is estimated based on the activity of primary users （PUs）. Therefore, available channels with estimated idle time longer than ETr could be chosen. With high probability, the SU can finish transmission on these channels without disruption, thereby satisfying the traffic load demand of the SU. Finally, our method is extended to the multi-channel scenario where each SU can access multiple channels simultaneously. Performance analysis shows that our method satisfies the requirement of SUs while effectively improving the throughput.     

Effects of sintering atmosphere on the physical and mechanical properties of modified BOF slag glass

This study proposes an efficient way to utilize all the chemical components of the basic oxygen furnace (BOF) slag to prepare high value-added glass-ceramics. A molten modified BOF slag was converted from the melting BOF slag by reducing it and separating out iron component in it, and the modified BOF slag was then quenched in water to form glasses with different basicities. The glasses were subsequently sintered in the temperature range of 600–1000℃ in air or nitrogen atmosphere for 1 h. The effects of different atmospheres on the physical and mechanical properties of sintered samples were studied by using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM) and by conducting experiment on evaluating the sintering shrinkage, water absorption and bulk density. It is found that the kinetics of the sintering process is significantly affected by sintering atmosphere. In particular, compared with sintering in air atmosphere, sintering in N₂ atmosphere promotes the synergistic growth of pyroxene and melilite crystalline phases, which can contribute to better mechanical properties and denser microstructure.     

Design and calculation of low infrared transmittance and low emissivity coatings for heat radiative applications

The infrared transmittance and emissivity of heat-insulating coatings pigmented with various structural particles were studied using Kubelka-Munk theory and Mie theory. The primary design purpose was to obtain the low transmittance and low emissivity coatings to reduce the heat transfer by thermal radiation for high-temperature applications. In the case of silica coating layers constituted with various structural titania particles (solid, hollow, and core-shell spherical), the dependence of transmittance and emissivity of the coating layer on the particle structure and the layer thickness was investigated and optimized. The results indicate that the coating pigmented with core-shell titania particles exhibits a lower infrared transmittance and a lower emissivity value than that with other structural particles and is suitable to radiative heat-insulating applications.     

Synthesis of BiOCl photocatalyst by a low-cost,simple hydrolytic technique and its excellent photocatalytic activity

A novel photocatalyst, bismuth oxychloride (BiOCl) micro-nano particles with a fine ferrite plate structure, was prepared by a low-cost, simple hydrolytic method. The as-prepared BiOCl was characterized by scanning electron microscopy (SEM), thermogravimetric analysis-differential thermal analysis (TGA-DTA), X-ray diffraction (XRD), and UV-vis diffuse reflectance spectra (DRS). The effects of preparation conditions such as sodium dodecyl benzene sulfonate (SDBS) dispersant, HCl concentration, and heat treatment temperature on BiOCl performances were investigated. Moreover, its photocatalytic activity was evaluated on the degradation of methylene orange (MO) and was compared with that of TiO₂ (P25). The experimental results confirmed that BiOCl micro-nano particles prepared with SDBS, the HCl concentration of 1.5 mol/L, and the heat treatment temperature of 80℃ exhibited the best performance for the photodegradation of MO solution, and they showed good stability and better photocatalytic activity than P25 photocatalyst.     

Electrochemical biosensors and logic devices based on aptamers

Aptamers are molecular recognition elements with high specificity that are selected from deoxyribonucleic acid/ribonucleic acid (DNA/RNA) library. Compared with the traditional protein recognition elements,aptamers have excellent properties such as cost-effective,stable,easy for synthesis and modification. In recent years,electrochemistry plays an important role in biosensor field because of its high sensitivity,high stability, fast response and easy miniaturization. Through the combination of these two technologies and our rational design,we constructed a series of biosensors and biochips that are simple,fast,cheap and miniaturized. Firstly,we designed an adenosine triphosphate (ATP) electrochemical biosensor based on the strand displacement strategy. We can detect as low as 10 nmol/L of ATP both in pure solution and complicated cell lysates. Secondly,we creatively split the aptamers into two fragments and constructed the sandwich assay platform only based on single aptamer sequence. We successfully transferred this design on biochips with multiple micro electrodes (6×6) and accomplished multiplex detection. In the fields of biochips and biocomputers,we designed several DNA logic gates with electric (electrochemical) signal as output which paves a new way for the development of DNA computer.     

Effects of anthropogenic disturbance on richness-dependent stability in Napahai plateau wetland

Unique plateau wetlands in China provide essential ecosystem functions and services and influence the health,environment and security of the downstream regions.In recent years,these plateau wetlands have experienced significant anthropogenic disturbance,but studies that evaluate the effects of such disturbance on ecological stability are rare.Our study tested how three typical types of human-related activities affect plant richness and ecological stability in Napahai plateau wetland,Shangri-La,China.The results showed that the anthropogenic disturbance had a direct effect on richness,and an indirect effect on stability mediated by richness.Anthropogenic disturbance did not alter the positive relationship between plant richness and community stability,and the stabilizing effect of richness could be explained by statistical averaging,overyielding effect,and component population stability.Our study complements previous studies that tested the richness-stability relationships in synthesized assemblages with richness specifically manipulated and studies that introduced mowing treatment to mimic real anthropogenic disturbance.The results further suggest that necessary steps,such as anthropogenic disturbance mitigation and plant richness conservation,are urgently required for maintaining healthy plateau wetlands and for sustaining their ecosystem functions and services.     

Energy conservation research of dehumidification system for main cable anticorrosion of suspension bridge

The necessity of the main cable anticorrosion for suspension bridge is described, and operating principles and composition of main cable dehumidification system are analyzed. An idea using the waste heat of high temperature outlet air of dehumidification system to heat up regeneration air of rotary-type dehumidifier is put forward in this paper. The concrete scheme is to install a heat exchanger on air-out pipeline of roots blower and air-in pipeline of regeneration electric heater of rotary dehumidifier. Air preheated by the heat exchanger enters regeneration electric heater of rotary-type dehumidifier. Energy conservation of main cable dehumidification system for the Yangtze River highway bridge is calculated, and the results show that energy conservation rate can reach 44 %.     

Effect of vanadium carbide on commercial pure aluminum

The effect of vanadium carbide (VC) on the grain size of commercial pure aluminum was experimentally investigated by varying the content of VC, the holding time, and casting temperature. The refining efficiencies of VC and Al5Ti1B were also compared. The refined samples of commercial pure aluminum were examined using optical microscopy, scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The results suggest that VC is a good refiner of commercial pure aluminum. The addition of only 0.3wt% VC can decrease the grain size of aluminum to 102 μm, whereas the casting temperature and holding time have little effect on the grain size. The refining efficiency of VC is better than that of Al5Ti1B. The VC particles in molten aluminum act as nuclei and the grain refinement of aluminum alloys by VC particles is achieved via heterogeneous nucleation.